etc. etc., then, no, your system is not suddenly crazy. Nor are you. It is highly likely that you RAM is defective. You should reboot your server and run the RAM test from your boot manager (Grub always has such a test) to see if it can detect faulty RAM.

If you are operating a server that you can’t reboot because you can’t tolerate downtime, there is an excellent tool called
memtester , which is a memory test for a running system. It is part of the Debian distribution, installit with
apt-get install memtester Check top to see how much free RAM there is available. Say you have 10GB RAM free, then ask memterst to test 8GB of it (so that 2GB are remaining free for the running system to operate). In my case, memtester indeed detected faults.